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Jens Rindel

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Papers by Jens Rindel

The Acoustical History of Hagia Sophia revived through Computer Simulation

Forum Acusticum Sevilla 2002 3rd European Congress on Acoustics Sevilla 2002 Isbn 8487985068, 2002

The present paper deals with acoustic computer simulations of Hagia Sophia, which is characterize... more The present paper deals with acoustic computer simulations of Hagia Sophia, which is characterized not only by being one of the largest worship buildings in the world, but also by -in its 1500 year history -having served three purposes: as a church, as a mosque and today as a museum. The investigation is done as a part of the EU project -CAHRISMA.

The Use Of A Digital Audio Mainframe For Room Acoustical Auralization

A new user-friendly method for auralization has been developed by interfacing a digital audio mai... more A new user-friendly method for auralization has been developed by interfacing a digital audio mainframe and a room acoustical computer model. Instead of using a convolution technique, early reflections are created by time delays and late reflections by an electronic reverberation processor. The system is verified through measurements of a number of room acoustical parameters on the terminals of the mainframe.

Lydisolering i bygninger - teori og vurdering

Sound insulation between dwellings – Descriptors applied in building regulations in Europe

Applied Acoustics, Mar 1, 2010

Regulatory sound insulation requirements for dwellings have existed since the 1950s in some count... more Regulatory sound insulation requirements for dwellings have existed since the 1950s in some countries and descriptors for evaluation of sound insulation have existed for nearly as long. However, the descriptors have changed considerably over time, from simple arithmetic averaging of frequency bands in the beginning, to a variety of more complex descriptors developed in different countries and later included in

Influence of Stud Distance on Sound Insulation of Gypsum Board Walls

Fundamentals of Acoustics and Noise Control

Directivity of musical instruments in a real performance situation

Measurements of the directivity of musical instruments are presented in the context of a new dire... more Measurements of the directivity of musical instruments are presented in the context of a new directivity representation of sources for auralizations. Three instruments have been recorded over the whole compass simultaneously in both horizontal and vertical planes with a multimicrophone array. Results are analyzed focusing on the differences between the directivity of particular tones and the averaged directivity over the whole compass. The consequences of these variations in a real performance situation in a room are looked into using computer room simulations. Further developments will consider room auralizations using different representations for the directivities of musical instruments.

Radiohuset, Studio 1, Copenhagen, Denmark

The acoustics of public squares/places: a comparison between results from a computer simulation program and measurements in situ

[176] In the context of a PhD thesis, in which the main purpose is to analyse the importance of t... more [176] In the context of a PhD thesis, in which the main purpose is to analyse the importance of the public square/place (“agora”) as a meeting pointof sound and music, with particular regard to its use for concerts (amplified or not), a first step was done, making comparisons between measurement in situ and results coming from a computer simulation

format_quoteThe simulation accuracy for reverberation time (T30) shows a good fit with measured values, suggesting effective predictive capabilities.format_quote

The virtual reconstruction of the ancient Roman concert hall in Aphrodisias, Turkey

The Alberta Jubilee Halls reborn with up-to-date acoustics

Perceived Speech Privacy in Computer Simulated Open-plan Offices

In open plan offices the lack of speech privacy between the workstations is one of the major acou... more In open plan offices the lack of speech privacy between the workstations is one of the major acoustic problems. Improving the speech privacy in an open plan design is therefore the main concern for a successful open plan environment. The project described in this paper aimed to investigate the relationships between the judged speech privacy and the objective acoustic parameters.

A study of pleasantness and annoyance in simulated soundscapes

An experimental study has been conducted in the Acoustic Technology Department of the Technical U... more An experimental study has been conducted in the Acoustic Technology Department of the Technical University of Denmark. Audio-visual simulations of a park and an urban square were attempted; a series of listening tests were carried out. The subjects were asked to qualify the soundscape in terms of both annoyance and pleasantness. Two sources were taken into account: Street Traffic Sound and Fountain Sound. The annoyance study concentrates in each source separately, whereas the pleasantness analysis focuses in combination of both sources. Figures of street traffic sound and water sound versus annoyance are presented. Furthermore, four different street traffic sound levels were used, whereas fountain sound level was varied. In all the presentations, birds sound has been included in order to make the acoustic environment more realistic. The pleasantness of different combinations of street traffic sound and fountain sound is illustrated.

Computer Modelling of Sound Fields in Rooms - the State of the Art and Outlook to the Future

Odeon, a Design Tool for Noise Control in Indoor Environments

SUMMARY Some rooms are much noisier than other, even with the same noise sources. For the design ... more SUMMARY Some rooms are much noisier than other, even with the same noise sources. For the design of low-noise indoor environments it is crucial that both the noise sources and the surrounding room surfaces are taken into account. Using a room acoustic computer model the first step is to model the room surfaces in terms of absorption and scattering properties. Next the sources are modelled, and while some sources may be sufficiently modelled by a simple point source, this is not sufficient for large noise sources. So, lines, surfaces and boxes should also be used for source modelling. In the design process the computer model offers a handful of tools like grid maps of noise distribution, reverberation time, spatial decay rate, identification of the most important sources, and possible effects of various noise control measures. Even the effect of sound insulating structures may be simulated. The methods and possibilities are demonstrated through a case of a large turbine hall with two...

Acoustical Computer Simulations of the Ancient Roman Theatres

The objective of this work (under WP5 of the ERATO project) has been to create and analyse acoust... more The objective of this work (under WP5 of the ERATO project) has been to create and analyse acoustical models of the selected theatres and odea by means of a computer simulation programme (named ODEON). Models have been created of the monuments both as originally built (to the extent that this is known), in their present state (as ruins), and with the temporary stages and scenery often applied when these spaces are used as performance venues today. Hereby, it has become possible to quantify the acoustical properties of the ancient theatres and odea in each condition leading to valuable information regarding the acoustical consequences and degree of authenticity of permanent restorations and temporary amendments. Moreover, based on recorded samples of authentic style music/speech (resulting from WPs 3 and 4), the simulations also have produced audible sound demonstrations of virtual performances with a high degree of acoustic realism. These sound files have been integrated with the visual restorations (WP 6) to form the audio in 3D virtual realizations of performances in the selected venues (WP7). The simulations of the acoustic conditions have been calibrated through comparison of the calculated results from the monuments in their present state with the actually measured acoustic data (from WP4). Also comparisons with the scale model studies contained in WP4 have ensured a high degree of accuracy in both modelling techniques supporting a deeper insight into the acoustics of ancient theatres and odea in general.

Auralisation of a Symphony Orchestra With Odeon - the Chain From Musical Instruments to the Eardrums

Auralisation is a very complicated technique, the quality of which depends on every single part i... more Auralisation is a very complicated technique, the quality of which depends on every single part in a long chain, starting with the anechoic recording of the sound to be used as input, continu- ing through the room acoustic simulation that connects the source and the receiver, and ending in the presentation of the sound to the listening person. The auralisation of a symphony orchestra is an even bigger challenge because of the large number of sound sources distrib- uted over a considerable area. Recently, a number of high quality anechoic recordings of symphonic music aiming at the multi- source auralisation technique have been available. So, the aim of this paper is to give an overview of the auralisation chain with particular reference to the multi-source auralisation of a sym- phony orchestra.

Predicting Acoustics in Class Rooms

Typical class rooms have fairly simple geometries, even so room acoustics in this type of room is... more Typical class rooms have fairly simple geometries, even so room acoustics in this type of room is difficult to predict using today’s room acoustics computer modeling,software. The reasons why acoustics of class room are harder to predict than acoustics of complicated concert halls might be explained by some typical features of these rooms; parallel walls, low ceiling height (the rooms are flat) and very uneven distribution of absorption. Itis suggested that a part ,of the ,explanation to the ,problem ,lies in the ,way ,scattering is implemented,in current models,relying on the,use of scattering coefficients that are used in order to describe ,surface scattering (roughness of material) as well ,scattering of reflected sound caused ,by limited ,surface size (diffraction). A method ,which ,combines ,scattering caused by diffraction due to surface dimensions, angle of incidence and incident path length with surface scattering is presented. Each of the ,two scattering effects is modeled ...

$If we assume energy conservation then we must also assume that the energy which is not reflected specularily has been diffracted - scattered due to diffraction. This leads to the following formula for our scattering coefficient due to diffraction: The attenuation factors K, and K,, are estimates to the fraction of energy which is reflected specularily. These factors take into account the incident and reflected path lengths (for ray tracing we have to assume that reflected path length equals incident path length) and angle of incidence. All information, which is not available before the calculation takes place.$

$As can be seen, scattering caused by diffraction is a function of a number of parameters some of which are not known before the actual calculation takes place. An example is that oblique angle of incidence lead to increased scattering whereas parallel walls lead to low scattering and sometimes flutter echoes. Another example is indicated by the characteristic distance a*, if source or receiver is close to a surface, this surface may provide a specular reflection even if its small, on the other hand, if far away it only provide scattered sound, s, =1.$

A study on the characteristics of phased beam tracing method for the acoustic simulation of an enclosure at mid frequencies

High frequency acoustic analysis of an enclosure has been dealt with by geometrical acoustic tech... more High frequency acoustic analysis of an enclosure has been dealt with by geometrical acoustic techniques and low frequency response can be estimated by modal methods; however, mid frequency range has been a grey zone. The phased beam tracing method (PBTM) is one of the mid-frequency techniques, which can calculate a pressure impulse response rather than energy reflectogram, although main assumptions in geometric acoustics still hold. The phased method utilizes the reflection coefficient representing the acoustic property of a surface and the complex wave number to describe the propagation characteristics. In this study, a room was chosen as a demonstration example and the proposed method was applied to this room; the result was compared with measurements.

$Research paper thumbnail of Diffraction around corners and over wide barriers in room acoustic simulations$

Diffraction around corners and over wide barriers in room acoustic simulations

The diffraction effects of screens and other obstacles have been integrated in a room acoustic co... more The diffraction effects of screens and other obstacles have been integrated in a room acoustic computer model using a theoretical model by Pierce, which is a further development of the original Geometrical Theory of Diffraction by Keller. This diffraction model is particularly interesting because it allows the modelling of a screen as a wedge with any opening angle, or as a wide barrier with two diffracting edges. Also the combination of two screens is possible. Another feature is that the model is valid even with the source or receiver located at the sur-face of the barrier. A major advantage of the method as implemented in the Odeon room acoustics software is the automatic detection and calculation of transmission paths around one or two edges. The basic assumptions, limitations, and examples of verification will be discussed.

$The contribution due to diffraction is calculated if the source is not visible from the receiver point and a propagation path with single or double diffraction can be found, see Fig. 1 and 2. The contribution is calculated for the shortest path of diffraction around the screen(s). The edge, for which diffraction is calculated, is regarded as infinitely long and therefore no other edges than the one describing the shortest path, will contribute to the calculation. In other words; no more than one diffraction path is used for each pair of source and receiver. This simplification has been chosen because the calculations in Odeon do not take the phase into account, and the phase would be im- portant if several diffracted contributions should be combined. Figure 1. Example of automatically detected propagation paths around one or two edges (two sources and one receiver).$

$Figure 3. A grid of SPL at 1000 Hz in a test-setup with a single point source, without and with the edge diffraction turned on.$